Multiple data formats may be transmitted over data lines in computer circuitry or communications systems. A receiving device or receiving user needs to know the data format of the received data to correctly decode the received data to acquire the information being transmitted. In some conventional systems, a type of communication line or circuitry line is determinative of the format of data being conveyed over that communication line or circuitry line. For example, when a Serial Advanced Technology Attachment or Serial-ATA hard drive is connected through a cable to a computer motherboard, the circuitry on the motherboard can expect that data transferred through the cable is formatted according to the specifications of the Serial-ATA interface.
In other conventional systems that have multi-purpose data lines or communications lines, extra information is transmitted along with the data and that extra information may be used to determine the encoding of received data. When the encoding is determined, the information in the data may be acquired. Digital audio data carried in a stream of ones and zeros that may be transmitted over a multi-purpose data line. For example, an audio data stream may carry multi-bit audio, such as Pulse Code Modulation (PCM) audio data, or single-bit audio, such as Direct Stream Digital (DSD) audio data. Both data formats appear as ones and zeroes on the data line, but undesirable noises may be generated by the speaker if the data is decoded according to the wrong standard. Conventionally, DSD data is marked to indicate when DSD data is transmitted over the line and PCM data is carried without any marking. One conventional manner of marking DSD data is shown in FIG. 1 for DSD over PCM (DoP). FIG. 1 is a data structure for DSD over PCM (DoP) audio data according to the prior art. A PCM data frame 100 is packed with a DSD payload 104 and a marker 102. The marker is conventionally a header attached to the DSD payload 104. An example 8-bit header is shown in FIG. 2. FIG. 2 is a data structure showing a header for marking DoP audio data according to the prior art. A marker 102 is placed in a data frame 200 before the DSD payload 104. However, this technique of using the header 102 reduces available bandwidth by adding overhead to the DSD data. In the example of FIG. 2 having an 8-bit header with a 16-bit DSD payload, the header 102 uses one-third of the bandwidth or imposes a 50% overhead penalty. This is undesirable at least because of the additional power consumed in a mobile device for transmitting this additional data.
Another conventional technique is to place marker information in a separate control line that accompanies the multi-purpose data line. The control line may include, for example, a binary indication of ‘1’ for DSD data and a ‘0’ for PCM data. However, this technique is also undesirable as the control line increases complexity of integrated circuit layouts.
Shortcomings mentioned here are only representative and are included simply to highlight that a need exists for improved electrical components, particularly for audio decoders and encoders employed in consumer-level devices, such as mobile phones. Embodiments described herein address certain shortcomings but not necessarily each and every one described here or known in the art. Furthermore, embodiments described herein may present other benefits than, and be used in other applications than, those of the shortcomings described above.